a) Field of the Invention
The present invention relates to a device for checking whether or not the optical axis of an automotive headlamp is correctly adjusted, and more specifically to an automotive headlamp optical-axis adjustment checker by which an index can be easily made to coincide with a reference point on a scale after the optical axis of the automotive headlamp is initially adjusted.
The automotive headlamps include generally two types: Movable-reflector type and movable-unit type. In a headlamp of the former type, a reflector to be adjusted is movably mounted on a lamp housing as a base member. In the latter-type headlamp, a lamp unit to be adjusted is movably mounted on a car body as a base member. For the simplicity of the explanation, it is assumed herein, unless otherwise specified, that the checker according to the present invention is to be installed on the lamp housing and the reflector is to be adjusted.
b) Description of the Prior Art
If directed too upward, the light beam from the automotive headlamp will dazzle the driver of a car running in the opposite lane, possibly causing a danger. On the contrary, if directed too downward, the headlamp will not provide a sufficient illumination of the road surface in front of the car for assurance of safe drive. Further, if the optical axis of the light beam from the headlamp is greatly shifted horizontally, the road surface in front of the car will not be appropriately illuminated, also causing a danger. To avoid such dangers, the optical axis of the automotive headlamp has to be correctly adjusted. Therefore, the automotive headlamp is provided with mechanisms fixed on the car body to adjust the optical axis a little vertically and horizontally.
One of the automotive headlamps of the above type is known from the disclosure in the U.S. Pat. No. 5,055,980. In this headlamp, a reflector is pivotably mounted on a lamp housing by means of a pivot bearing, a lamp bulb is provided in the reflector, and the reflector and lamp housing have mounted therein mechanism for adjusting the optical axis of the headlamp vertically and a one for adjusting the optical axis horizontally.
Such an optical-axis adjusting mechanism comprises an adjusting screw mounted in the lamp housing rotatably but not axially movably, etc. By operating the adjusting screw of the above-mentioned vertical optical-axis adjusting mechanism or that of the horizontal optical-axis adjusting mechanism, the reflector is pivoted vertically or horizontally in relation to the lamp housing for vertical or horizontal adjustment of the optical axis.
The direction of the headlamp optical axis must be adjusted elaborately with a high accuracy and can be adjusted only by a specialist using a special equipment. Therefore, before shipment of a car from the automobile manufacturing works or when the headlamps are equipped on a car at a service shop, the optical axes of the headlamps are initially adjusted by the specialist there with the special equipment.
After the optical axes of the headlamps of a car are initially adjusted, it becomes necessary for some reason to readjust the optical axes. The optical-axis readjustment is done while ascertaining, by using an optical-axis adjustment checker, how much the optical axis is to be adjusted.
Various optical-axis adjustment checking devices have been proposed so far. One of such devices is disclosed in the U.S. Pat. No. 5,068,769. The device comprises a pointer so mounted on an adjusting screw as to be movable axially of the adjusting screw as the latter is turned, and a scale plate so mounted on a lamp housing as to be movable axially of the screw.
When the adjusting screw of the optical-axis adjustment checking device is turned to pivot the reflector vertically or horizontally in relation to the lamp housing for vertical or horizontal adjustment of the optical axis, the pointer is moved axially of the adjusting screw as the latter is turned. This movement of the pointer is readable as a deviation between an index on the pointer and a mating-index on the scale plate. Namely, it is a required mount of optical-axis adjustment. Thus, the optical axis of the headlamp, that is, of the reflector can be adjusted based on the thus-read or necessary amount of optical-axis adjustment.
In the above-mentioned optical-axis adjustment checking device, however, since the pointer is so mounted on the adjusting screw as to be moved axially of the adjusting screw as the latter is turned, turning the adjusting screw for initial adjustment of the reflector optical axis causes the pointer to be moved axially of the adjusting screw. Therefore, after completion of that initial adjustment, it is necessary to make the index on the pointer coincide with the "0" or mating-index on the scale plate by moving the scale plate axially of the adjusting screw.
Also, the above-mentioned device has a first and second gears in mesh with each other and a spring which normally forces the second gear for engagement with the second gear. So, the initial adjustment of reflector optical axis has to be done by turning the adjusting screw while keeping the first and second gears disengaged from each other, by pressing the second gear against the force of the spring, so that the second gear will not be rotated.